© 1987 by Biometrika Trust
On multivariate ridge regression
Departments of Statistics and Economics, Hebrew University of Jerusalem Jerusalem 91905, Israel
A multivariate linear regression model with q responses as a linear function of p independent variables is considered with a p × q parameter matrix B. The least-squares or normal-theory maximum likelihood estimate of B is deficient in that it takes no account of the across regression correlations, and ignores the Stein effect. A remedy was offered by Brown & Zidek (1980) in the form of a multivariate ridge estimator. A richer class of estimators is obtained here by casting the model in a linear hierarchical framework, obtaining the Brown & Zidek multivariate ridge estimates, Efron & Morris's estimates of several normal mean vectors and Fearn's Bayesian estimates of growth curves as special cases. The unknown covariance case results in an identifiability problem, which can be overcome by a Bayesian approach using conjugate priors for the unidentified covariance matrices.
Key Words: Bayes estimates EM algorithm Exchangeability Lindley-Smith modal estimate Linear hierarchical model Maximum likelihood Mean of multivariate normal distribution Multivariate regression Ridge regression Stein estimator